1. Field of the Invention
The present invention concerns a tire with radial carcass reinforcement intended to be mounted on a rim, at least one seat of which is inclined towards the outside and is extended axially to the outside by a low projection. It concerns more particularly the beads of such a tire.
2. Description of the Related Prior Art
A bead intended to be mounted on a rim, at least one seat of which is inclined towards the outside, is described for example in the international publication WO 95/23073. The rim described in this publication comprises an external wall whose portion axially towards the outside is axially recessed with respect to the low projection on the rim. Consequently, this rim part axially furthest towards the outside does not benefit from any protection by the tire against attacks caused, for example, by rubbing against pavements during travel in town. The architecture, that is to say the structure, of this type of tire rim is described in the international publication WO 95/23073 and comprises in particular a part forming a “heel” designed so as to be situated axially towards the inside and a bead toe designed so as to be situated axially towards the outside when the tire is mounted on its mounting rim.
This tire also comprises a carcass reinforcement, the ends of which are anchored in each bead to an anchoring device, the said anchoring device being formed from at least one circumferential rim reinforcement element (such as a bead wire or a set of wires or cables wound circumferentially) and a wedge made from a mixture of high-hardness rubber and substantially triangular in shape. This wedge is, seen in section in a meridian plane (that is to say a plane containing the rotation axis of the tire), delimited by a radially external lateral face and a radially internal face and finally a face connecting the above two faces and situated axially to the outside, so that the vertex of the wedge opposite to the said lateral face is situated radially towards the inside of the circumferential bead reinforcement. The carcass reinforcement is anchored at each of its ends on the said anchoring device by means of an upturn which, at least partially, winds around the circumferential bead reinforcement element and is extended in or around the wedge made from a mixture of high-hardness rubber.
The fact that it is wished to provide satisfactory protection of the rim against various impacts and friction has led to adapting the axially external shape of the bead, an adaptation consisting of providing an addition volume of rubber mixture so that this additional volume prevents contact of the axial external projection on the rim with any external object.
Though this additional volume, forming a protuberance on each bead mounted on a rim seat inclined towards the outside, effectively protects the corresponding projection on the rim, it is of course liable to be subjected to a phenomenon of abrasion when the tire rubs against an external object, in particular a pavement. International application WO 99/64258 published on 16 Dec. 1999 teaches providing this protuberance with a plurality of incisions of non-zero width and with a depth of no more than 5 mm, these incisions delimiting a plurality of ribs parallel to each other and spaced apart evenly in the circumferential direction.
This latter construction, though it is favorable with regard to the abrasion aspect, nevertheless still presents a few drawbacks which the present invention seeks to resolve. This is because it has been found that, under extreme conditions, detachment of localized material could occur over a greater or lesser thickness. In certain cases, the thickness is such that the wedge of the anchoring device is laid bare and possibly the reinforcements of the carcass reinforcement are also. The carcass reinforcements are then no longer protected from external agents (water, air etc).